Positive end-expiratory pressure alters the severity and spatial heterogeneity of ventilator-induced lung injury: An argument for cyclical airway collapse

Abstract

PurposeVentilator-induced lung injury (VILI) is a recognized complication of mechanical ventilation. Although the specific mechanism by which mechanical ventilation causes lung injury remains an active area of study, both alveolar overdistension and cyclical airway collapse and recruitment have been suggested as contributing causes. We hypothesized that mechanical ventilation in the absence of positive end-expiratory pressure (PEEP) causes VILI to be more severe and regionally variable as compared with PEEP = 8 cm H2O. Materials and MethodsTo test this hypothesis, anesthetized, supine rabbits were mechanically ventilated with an end-inspiratory pressure of 28 cm H2O and either 0 or 8 cm H2O PEEP for 4 hours. Regional lung injury was determined by histologic scoring. ResultsIn the absence of PEEP, lung injury was regionally variable and greatest in the dorsal-caudal lung. This regional injury heterogeneity was abolished by the addition of PEEP = 8 cm H2O. ConclusionsThese results suggest that VILI is regionally heterogeneous and spatially correlates with regions in which cyclical airway collapse and recruitment is most likely to occur.